Radiation detectors have been used in security, defense, safety, scientific, medical and industrial applications and may detect many types of ionizing radiation, e.g., gamma rays, X-rays, and nuclear particles. One particularly critical use for radiation detectors is for security, for example, cargo inspection to guard against terrorist smuggling a dirty bomb or other radioactive material in commercial shipments, but radiation detectors are not limited to use for cargo inspection or even security applications. More generally, individual radiation detectors and networks of radiation detectors may be widely needed, for example, for securing national borders, as part of the regular inventory of law enforcement agencies and fire departments, and for installations or use at transportation hubs, entertainment venues, road intersections, or any populated areas, for detection of dangerous or illicit radioactive material.
Radiation detectors in many applications may not only need to detect radioactive materials but may also need to identify or differentiate materials, for example, to avoid triggering false alarms. In particular, a radiation detector may need to distinguish illicit or dangerous radioactive materials from naturally-occurring radioactive material or medical isotopes. Isotope identification through emission spectrum analysis is possible but may require expensive gamma-ray detectors with high energy resolution and a wide detection bandwidth covering both low and high energy gamma-rays. Neutron detectors, which are important in scientific research and nuclear reactor operation, may also distinguish illicit radioactive material because few naturally occurring materials emit neutrons. The most common type of neutron detectors currently uses pressurized tubes containing helium-3 gas and are typically bulky, costly, and difficult to configure.
Satisfying the growing need for radiation detectors may require low-cost, room-temperature operation, high energy resolution, and high-efficiency detection of ionizing radiation including gamma-rays and nuclear particles.